Over the years, numerous devices for electric underwater propulsion for scuba divers have been developed. Some of these involve the scuba diver holding the device in his hands, whereas other solutions involve the attaching of the propulsion system to the scuba diver's equipment.
A problem with hand held devices is that they fatigue the scuba diver's arms inasmuch as he has to "hang on" as he is pulled through the water. Another problem with prior art components is that they restrict the scuba diver's ability to function "hands free" since he must carry the device.
Yet another problem is that it restricts a scuba diver's mobility since he must be able to let go of the device in order to use his hands. In this instance, the diver must be able to, in some fashion, secure the device by resting it in some suitable place, or tethering it to something.
Problems also exist with propulsion devices that attach to a scuba diver's equipment, for in order for these mounted devices to function properly, the scuba diver must face a number of sacrifices and restrictions. For example, it is known that a properly weighted scuba diver is almost neutrally buoyant when he is at the surface of the water. Any additional equipment that he carries such as a propulsion device, must also be approximately neutrally buoyant, so as not to upset this balance. For the propulsion device to be near neutrally buoyant it must displace, when submerged, an amount of water almost equal to its weight. Hence, the volume and weight are directly proportional.
An initial problem encountered when attaching a propulsion device to a scuba diver's equipment is how to offset the weight of the device while keeping the bulk to a minimum. One solution would be to reduce the size of the scuba diver's air tank, to make room for the additional volume needed to offset the weight of the propulsion device. This approach was recognized by the Strader U.S. Pat. No. 3,329,118 and the Galimand U.S. Pat. No. 4,753,187. However, this reduction in the volume of compressed air carried severely limits the amount of time the scuba diver can stay submerged. This problem is solved by using a more efficient battery such as the kind used in McCullough U.S. Pat. No. 3,995,578 as well as Strader '118. This approach becomes impractical, however, in terms of economics and battery cycle life. Another option is just to use a smaller, less expensive battery, possibly in conjunction with a smaller motor, as did Bardoni et al in their U.S. Pat. No. 3,916,814. In this latter instance, the diver would have to settle for less performance.
Another solution would be to reduce the size and weight of the battery. The problem here is that a practical, rechargeable battery such as a sealed lead-acid battery has low energy density, meaning that a smaller and lighter battery has less power. This of course results in reduced operating time for the device. Therefore, to obtain a reasonable operating time for the device, the excessive weight and size of the more practical battery must be incurred.
A novel solution to this problem was the recognition of the fact that scuba divers wear leaded weight belts in order to achieve a near neutral buoyancy at the surface of the water. It can be reasoned therefore, that the battery pack for the propulsion device could be used in lieu of the lead weights to accomplish the desired balance. This approach was recognized by Parker U.S. Pat. No. 4,843,998. A problem exists, however, with regard to the approach set forth in the Parker patent, which is that not all divers require the same amount of weight to obtain the desired buoyancy. A smaller scuba diver needs less weight to submerge than a larger one, and the size of the wetsuit a diver may or may not use also effects this condition.
Therefore, some divers may be forced to wear a smaller battery pack so as not to upset his or her weight balance in the water. Again, this reduces the operating time of the propulsion device.
Another problem is the proper location of the propulsion device that is attached to scuba diver's equipment. Having the propulsion device mounted longitudinally parallel to the diver's air tank, but laterally displaced therefrom gives way to at least two undesirable effects.
One undesirable effect is that the center of thrust is further removed from the diver's center of gravity. This means that the thrust line must be redirected so as to reside at a greater angle towards the diver in order for him to achieve a more horizontal motion when traveling forward through the water. Still another problem is the larger silhouette created by this location.
Ideally, the propulsion device should be placed in a position such that the thrust line is laterally displaced from the diver's center of gravity to the smallest extent possible. Various attempts to take this into consideration can be noted from the configurations of the devices taught by Fogarty U.S. Pat. No. 3,014,448, Pestronk U.S. Pat. No. 3,034,467, Schultz U.S. Pat. No. 3,128,739 and Strader '118.
The Cameron et al U.S. Pat. No. 4,996,938 captioned "Apparatus for Propelling a User in an Underwater Environment," bears some relationship to the instant invention, but it is to be immediately noted that the user of the Cameron et al device must at all times be using both hands for holding and controlling the apparatus. This is of course a distinct disadvantage to any diver needing both hands free for completing other tasks.
Another important point is that Cameron et al apparently has wasted space in their hull assembly 12, for the diver still has to carry conventional air tanks on his back. This of course is a disadvantage when compared with the use of an air tank serving the multiple purposes of supplying breathable air for the diver as well as in serving as a structural mounting for the propulsion components.
Still another important point is that in Cameron et al patent, there is no provision for locking the motor and propellers in a fixed relationship to the diver.
Whereas all of the devices mentioned hereinabove present a distinct impracticality in some aspect of their design, involving one or more problems with economics, configuration, weight, and/or performance, my highly advantageous configuration for a diver's underwater propulsion system overcomes these problems in a highly satisfactory manner.